If I were you, I would try a 5k program. Are you brand new to running? The Couch to 5k is a great program and there are many other similar plans out there.

Start small and and keep increasing your distance little by little. You will need a lot more than just 12 weeks to train for a half if you are starting from scratch. I started running last August and will be doing my first half marathon in December. I've done countless 5ks, a 10k, and a mud run/obstacle course over that last year. I'm in the process of training for my half and still have "Can I really do this??" moments. I don't mean to discourage you because I'm sure you can do it if you really want it, I would just hate for you to get in over your head and get hurt or frustrated. Check out the Runner's World website. There is a forum there with lots of help for beginners.

Can you run in the early am before your DH goes to work or in the evening when he gets home? I only run outside and have no treadmill experience so I can't really speak to that.

Good luck and keep us updated! And congrats on the weight loss and getting started on an exercise plan. The first step is always the hardest.